1Department of Laboratory Medicine, The Catholic University of Korea, Uijeongbu St. Mary’s Hospital, Seoul, Korea; 2Department of Laboratory Medicine, Hallym University College of Medicine, Hwaseong, Korea; Departments of 3Laboratory Medicine, 4Radiology, and 5Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

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Abstract

Background: Krebs von den Lungen 6 (KL-6) is a sensitive marker for diagnosing, monitoring, and predicting the prognoses of interstitial lung diseases (ILDs). This study aimed to evaluate the performance of the Nanopia KL-6 assay (Sekisui Medical, Tokyo, Japan) and to test the relationship between KL-6 concentrations and clinical results. Methods: In total, 230 patients diagnosed as having ILDs were enrolled. All underwent high-resolution computed tomography (HRCT) followed by the pulmonary function test (PFT). We also enrolled 116 disease controls and 200 healthy controls. Evaluation of the Nanopia KL-6 assay involved determination of precision, linearity, and limit of quantification (LOQ). Results from the Nanopia KL-6 assay were compared with those from ELISA and correlated with the HRCT and PFT results. Results: The within-laboratory precisions were <2% of CV, and linearity was acceptable between 52.2 and 4,966.5 U/mL. The LOQ was 45.2 U/mL. Nanopia and ELISA results were strongly correlated (r=0.979). The average concentration of KL-6 was greater in ILD patients (711.5 U/mL) than in the disease (168.4 U/mL) and healthy (209.4 U/mL) controls. Serum KL-6 concentrations were strongly and moderately correlated with the extent of lung involvement and presence of typical HRCT abnormalities, respectively, and moderately correlated with PFT parameters. Conclusions: The overall analytical and clinical performance of the Nanopia KL-6 assay was acceptable. Our study is the first to compare assay platforms and show correlations between KL-6 concentrations and HRCT or PFT results in Korean ILD patients.